There are conflicting reports regarding the adverse effects of Vitamin D (Vit D) deficiency on several major chronic diseases, such as coronary heart disease (CHD) and cancer. It is reported that hypovitaminosis D is widespread, the elderly being particularly susceptible. The main source of Vit D in North America is through sunlight exposure. The emphasis placed on protection from sunlight exposure to reduce skin cancer risk may be creating an increased risk for CHD. By using the Adventist Health Study-2 questionnaire data and its 100,000 subjects countrywide, we intend to further elucidate the relationships between serum 25 hydroxy Vit D(25-OH-D) (the best indicator of vit D status) and fatal CHD and total mortality after 5 years follow-up. We will use blood samples collected for the calibration study to determine actual serum Vit D levels. Regression calibration will then be used to predict expected values of serum 25 hydroxy Vit D conditional on exposures to dietary vit D, calcium intake, sunlight, and age. Results for blacks will be compared to those of "whites" because skin pigmentation reduces the amount of the active form of Vit D converted from precursors.